What is ReactJS Reconciliation?

ReactJS is perhaps one of the top frameworks known for the development of highly responsive UIs. Compared to other JavaScript frameworks, it is very efficient when it comes to dealing with complicated layouts. The secret to this lies in the reconciliation process that React has. Reconciliation in React can be defined as how React updates the UI of an application when changes happen. This process is made to make sure that the UI remains engaged and only the part or component that needs to be updated is updated, hence making the entire process faster and easier.

In this blog, you will get to know about the working concept of ReactJS reconciliation, which comprises a virtual DOM and a diffing algorithm that makes React powerful. By the end of the lesson, you will know how the React updates work without having to refresh the entire page.

ReactJS Reconciliation Working Concepts

Reconciliation is the mechanism by which React determines which parts of the user interface have to be updated in reaction to changes in the application state. It identifies which components are dynamic and therefore decides to alter only that section of the DOM that requires it.

At the core of this process are two important concepts:

• The Virtual DOM
• The diffing algorithm

It may be helpful to take a closer look at each of these ideas in detail so as to determine their role in the process of reconciliation in React.

Virtual DOM

As for traditional web applications, every time there is a change in the data, the entire DOM is rerendered. This may be time-consuming and costly, particularly for large web applications that are complicated to manage. React solves this problem with the help of a concept called the Virtual DOM.

What is the Virtual DOM?

It can be described as a replica of the actual DOM tree that is, however, much lighter. Whenever the state or data of a React application changes, React actually builds a completely new virtual DOM instead of directly altering the real DOM. This can be compared to a twin brother of the real DOM; however, this one is not as obvious to the user. What remains is only a memory. Memory of Abor decided to lay in the middle of the door as it only exists in memory.

Here’s how the Virtual DOM works:

• React saves the copy of the browser’s DOM tree in its memory and calls it the virtual DOM.
• Suppose you modify or modify some data inside an application; in turn, React develops a new virtual DOM based on new updates.
• This makes React work out what has changed between the two versions of the virtual DOM by way of comparison.
• React then computes the minimum number of changes that have to be made to the browser’s actual DOM, then updates only those parts that it has found to be changed and not changes the entire DOM.

This increased the render time so much because React reduces the amount of effort required for altering the real DOM. The means, through the virtual DOM, React can handle the changes even if the number of nodes in the DOM is ten thousand.

If you’re looking to dive deeper into the Virtual DOM concept and how it enhances the performance of React applications, consider enrolling in this React JS Course.

Benefits of the Virtual DOM

• Performance Optimization: The Virtual DOM ensures that the browser’s real DOM is only updated when absolutely necessary, reducing the number of costly DOM manipulations.

• Faster Rendering: Since React only updates the parts of the DOM that have changed, it results in faster page loads and smoother user interactions.

• Efficient Resource Usage: By minimizing the number of updates to the real DOM, React reduces the computational resources required to keep the UI up to date.

Diffing Algorithm

The Diffing Algorithm is one of the important parts of React and its reconciliation process. Whenever there are changes on the application, React checks the new virtual DOM with the older one in order to identify the differences. This is done through the diffing algorithm.

How the Diffing Algorithm Works

The responsibility of identifying what needs to be updated lies in the diffing algorithm, which is efficient in comparing the two versions of the virtual DOM. Here’s how it works:

• React forces the creation of the new virtual DOM whenever the state or the data involved in the running app alters.
• It contrasts this new version with the previous version of the Virtual DOM.
• The Diffing Algorithm is where the Angular JS determines the variation between the two versions and highlights the parts of the DOM that it finds were changed.
• Then it sends down only the parts of the actual DOM which are different from the current page and hence it does not refresh the whole page like a traditional web page.

This is far faster than the earlier method of having to update the entire DOM every time there would be a change. React can renovate large and complicated transformers in a blink of an eye and therefore is suitable for dynamic web applications.

Key Concepts of the Diffing Algorithm

The Diffing Algorithm uses several key concepts to optimize the reconciliation process:

• Two elements of different types produce different trees: If React finds that two elements are of different types, for example, changing a <div> to <span>, then it will replace the whole tree of the old element with a new tree of the new element.
• Breadth-First Search (BFS): React employs the process of BFS in order to search for the Virtual DOM tree. This makes it easier if a change is to be made in a node of the tree as the whole subtree will be rendered again according to the need, hence more efficient in terms of updates.
• Keeping the same type of elements: When comparing two elements of the same type, React maintains the DOM node ID remains the same, whereas the attributes and styles may have been updated.

Through the use of these concepts, React makes a guarantee that any differences between the two versions of the virtual DOM are done in O(N) time, making it cost-effective, especially for complex applications.

FAQs

What is reconciliation in ReactJS?

Reconciliation is the way React optimizes the update of the user interface. Virtual DOM – works similarly to the previous version by comparing the new virtual DOM and updating the real DOM only where changes occurred.

What is the difference between diffing and reconciliation?

It’s important to note that Diffing is the action of determining what has changed between VDOMs and Reconciliation is the process of applying the resulting diff to the real DOM.

What is Virtual DOM and reconciliation?

The Virtual DOM is a lightweight copy of the real DOM used to manage updates efficiently. Reconciliation is the process that updates the real DOM after comparing old and new Virtual DOMs.

What is React Fiber and reconciliation?

React Fiber is a rewrite of React’s rendering engine that optimizes UI updates. It enhances reconciliation by allowing React to prioritize and manage updates more efficiently.